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It is important to understand that both safe operation and maintenance are key to avoiding disaster. Dam failures can and have occurred in the U.S., causing loss of life and severe economic and environmental damage.

The average age of the 90,580 dams in the country is 56 years. As our population grows and development continues, the overall number of high-hazard potential dams (those whose failure could cause loss of life) increases as well, with the number climbing to nearly 15,500 high-hazard potential dams in 2016. Another 11,882 dams are currently labeled as significant-hazard potential, meaning a failure would not necessarily cause a loss of life, but could result in significant economic losses.

The number of deficient dams is likewise climbing. A majority of states and federal agencies define a deficient dam as one that has been found to have hydraulic or structural deficiencies that leave it more susceptible to failure. Due to a lack of investment in maintenance, the number of deficient high-hazard potential dams has climbed to an estimated 2,170. ASDSO estimates that it would take an investment of $18.71 billion to rehabilitate all of the non-federal high-hazard dams in the United States.* According to the ASCE 2016 Report Card**, the U.S. Army Corps of Engineers estimates that more than $25 billion will be required to address dam deficiencies for Corps-owned dams. At current investment rates, these repairs would take over 50 years to complete. The Bureau of Reclamation has identified approximately 20 of its high- and significant-hazard potential dams as in need of repair or upgrade. The cost of these actions is estimated at $2 billion over the next 15 years.

*The full report for this research is available for download at the "In This Section" widget at the top of the page.
**The full ASCE Report Card is available for download at the "In This Section" widget at the top of the page.

Lack of financing for and attention to maintenance, upgrade and repair

Lack of adequate authority and resources for state dam safety programs

Lack of emergency preparedness in case of failure

Lack of public awareness

Risk of Failure
Driving every other issue and all activities within the dam safety community is the risk of dam failure. Although the majority of dams in the U.S. have responsible owners and are properly maintained, many dams still fail every year. From Januay 2005 to June 2013, states have reported 173 dam failures and 587 'incidents' - episodes that, without intervention, would likely have resulted in a failure. Dam and downstream repair costs resulting from failures in 23 states reporting in once recent year totaled $54.3 million.

Historically, dams that failed had some deficiency, which caused the failure. Currently, the number of deficient high-hazard potential dams is more than 2,170. There are deficient dams in almost every state. The risk of failure only increases as dams across the nation age. Currently, the average age of dams in the United States is 56 years. By 2025, 7 out of 19 dams will be over 50 years old. Without the needed upgrades and rehabilitation, these dams cannot be expected to withstand current flood and earthquake predictions.

Increasing Hazard
Dams are innately hazardous structures. Failure or mis-operation can result in the release of the reservoir contents - this includes water, mine wastes, or agricultural refuse - causing negative impacts upstream or downstream or at locations remote from the dam. Negative impacts of primary concern are the loss of human life, economic loss including property damage, lifeline disruption and environmental damage.

Some dams are considered to have a greater hazard potential than others. As of 2016, there are approximately 15,500 high-hazard potential dams in the United States. "High-hazard potential" is a term used by a majority of state dam safety programs and federal agencies as part of a three-pronged classification system used to determine how hazardous a dam's failure might be to the downstream area.

While the definitionvaries from place to place, it generally means if failure of a high-hazard dam occurs, there probably will be loss of life. It must be emphasized that this determination does not mean that these dams are in need of repair - these dams could be in excellent condition or they could be in poor condition. High-hazard just reflects the dam's potential for doing damage downstream should it ever fail.

High-hazard potential dams exist in every state and affect the lives of thousands downstream. The current issue and debate is over the increasing number of these high-hazard structures - not because more high-hazard dams are being built, but that more development is occuring downstream. Dam safety regulators generally have no control over local zoning issues or developers' property rights, and so this issue continues to worry regulators as the "hazard creep" trend persists.

Lack of Financing for and Attention to Maintenance, Upgrade, and Repair
Dams must be maintained to keep them safe. Occasional upgrade or rehabilitation is necessary due to deterioration, changing technical standards, improved techniques, better understanding of the area's precipitation conditions, and changes in downstream populations or land use. When a dam's hazard classification is changed to reflect and increased hazard potential, the dam may need to be upgraded to meet an increased need for safety. The age of a dam is not necessarily a direct indicator of its condition. Age is indirectly an indicator in that old dams were not built to the standards of today. Some older dams are considered in poor condition for this reason alone, while others may have been inadequately maintained as well.

In 2017, the American Society of Civil Engineers updates its Infrastructure Report Card. In this report, dam safety was given a 'D', the same grade it received in 2013. This is mostly due to the number of deficient high-hazard dams and the lack of funding the sector currently receives. The full report is available here.

Private ownership makes dams a unique part of the national infrastructure. While most infrastructure facilities (roads, bridges, sewer systems, etc.) are owned by public entities, the majority of dams in the United States are privately owned. A dam's owner is solely responsible for the safety and liability of the dam and for financing its upkeep, upgrade, and repair.

Many different types of people and entities own and operate dams:

Private ownership (about 64% of dams)

Local governments (about 20% of dams)

State agencies (about 7 percent)

Federal government, public entities, and other undetermined interests own the remainder

Lack of funding for dam upgradesis a serious national problem, especially within the private sector. Operation, maintenance, and rehabilitation of dams can range in cost from the low thousands to millions, and responsibility for these expenses lies with owners, many of whom cannot afford these costs. Although some states offer loan programs, for the most part funding assistance through either government or private sources is minimal at best.

According toa 2016 ASDSO study, the combined total cost to rehabilitate the nation's non-federal and federal dams exceeds $64 billion. To rehabilitate the nation's more critical, high-hazard potential dams would cost nearly $22 billion. WIthout financing for maintenance and repair, the cost of rehabilitation will only climb higher.

Lack of Adequate Authority and Resources for State Dam Safety Programs
States are responsible for oversight of the vast majority of dams listed in the National Inventory of Dams. Although most states have legislative authority to carry out a comprehensive dam safety program, many are lacking in specific areas. Some states are unable, by specific language in their law, to regulate certain types of dams, allowing these structures to fall between the regulatory cracks. Other states have limited ability to enforce the law. In some states, officials have no recourse if dam owners do not carry out safety repairs ordered by the state.

Many states are simply under-resourced for carrying out the letter of the law. In FY 2018, state budgets for dam safety range from $0 (Alabama) to $21.3 million (California - includes a one-time budget increase in FY2018 primarily due to a $6.5 million General Fund loan for 12 new positions for the new inundation mapping program and spillway re-evaluation program). But the average annual state dam safety budget is about $1.18 million. The average number of regulated dams per state is about 1600. The average number of dam inspectors per state is about eight. This means that each dam inspector is responsible for overseeing the safety of about 200 existing dams, plus the additional responsibilities of overseeing new construction.

There is, therefore, a serious need in almost every state to pump additional state resources into these programs.

Lack of Emergency Preparedness in Case of Failure
Emergency preparedness is improving, with the percentage of state-regulated high-hazard potential dams with an Emergency Action Plan (EAP) increasing from 35% to 81% between 1999 and 2017. The goal is for all high-hazard potential dams to have an EAP so that dam owners and local authorities are prepared for a sudden dam failure and the ensuing downstream consequences.

Lack of Public Awareness
Intersecting almost all the issues above is the issue of public education about dams. The ordinary citizen is unaware that the beautiful lakes on which they boat, ski, or fish are only there because of manmade dams. Developers build in dam-break flood inundation areas knowing nothing about the potential devastation an upstream dam could cause should it ever fail. In fact, some developers and zoning officials are completely unaware of dams within their community. Even if citizens understand and are aware of dams, they still can be overly confident in the infallibility of these manmade structures. Living in dam-break flood-prone areas is a risk.

Many dam owners do not realize their responsibility and liability toward the downstream public and environment. Adequate understanding of proper dam maintenance and upgrade techniques is a typical problem among many owners across the United States.

Some groups put forth the message that dams are bad for the environment and advocate their removal. This may mislead the public into thinking that taking care of our dams is a worthless cause. In some cases, dam removal is the beset solution, but in all instances the consequences should be considered before coming to this decision.

State Dam Safety Program Statistics
States have permitting, inspection, and enforcement authority for 70% of the 90,580 dams listed in the 2016 National Inventory of Dams (NID). More state and national statistics are available from their website.

Graph 1

Graph 2

Graph 3

Graph 4

Graph 5

Graph 6

Graph 7

Graph 8

Graph 9

Some important statistics to note:

Most dams listed in the NID are classified as low-hazard potential (Graph 1).

Total budgets for state dam safety programs have rebounded somewhat from the 2008 economic downturn when many programs experienced cuts in funding as state budgets struggled in general (Graph 3) (Graph 4). Staffing did see an increase in 2017 (following a slight decrease in 2015), and it has remained relatively steady in recent years with an overall increasing trend since 1999 (Graph 5).

State by state statistics and information about state-specific dam regulators are available in the 2016 State Dam Safety Program Statistics and State Dam Safety Performance Reports, which can be accessed through our state map.

Building State Programs to Address Deficient Dams
The National Dam Safety Program, in cooperation with ASDSO, developed the Model State Dam Safety Program to assist state officials in initiating or improving their state programs. The model outlines the key components of an effective dam safety program and provides guidance on the development of more effective and sustainable state programs to minimize risks created by unsafe dams. It contains chapters on Legislative Authorities, Permitting, Inspection, Enforcement, Emergency Action Planning and Response, Education and Training, and Public Relations.

The table below presents the weighted average of state responses over time to a series of yes/no questions on the authorities of each chapter. The areas are listed and weighted by importance (weights indicated in parentheses). Higher percentages indicate greater alignment with the model. The overall increased percentages since 1989 demonstrate significant progress by state programs in these areas.

State Compliance

State Compliance

1989

1998

2010

2018

Legislation (5)

64%

73%

85%

86%

Inspection (4)

54%

68%

74%

78%

Enforcement (4)

66%

79%

90%

92%

EAP & Response (4)

51%

62%

72%

78%

Permitting (3)

58%

67%

75%

76%

Education & Training (3)

59%

72%

75%

Public Relations (1)

13%

30%

31%

Weighted Percentage

59%

66%

77%

79%

Emergency Action Plans (EAPs) for High-Hazard Potential Dams
Nationally, the percentage of state-regulated high-hazard potential dams with an EAP has increased from 35% to 81% for the period of 1999 to 2017. Nearly every state has shown improvement in the number of EAPs for high-hazard potential dams with no state showing a significant decrease. Many states had increases of several hundred to several thousand percent.

Within that period, the average of individual state increases in EAPs was 740%; Hawaii had the greatest improvement (6100% increase, going from just 2 EAPs in 1999 to 124 in 2017). In just the last ten reporting years (2008-2017) the average of state increases was 183% (as an example, Texas increased from 163 EAPs in 2008 to 1,083 in 2017, an increase of over 560%).

In 2017, 29 states reported that 90% or greater of their high-hazard potential dams had an Emergency Action Plan, up from just ten states in 1999. However, there is still room for improvement, with five states reporting that less than half of their high-hazard potential dams have an Emergency Action Plan prepared (Graph 6 and Graph 7).

Inspections of High-Hazard Potential Dams
Graph 7 shows the percentage of inspections completed for high-hazard potential dams based on the inspection frequency and schedule due for a particular state. Inspection percentages may vary above and below 100% for any given year based on a state's inspection frequency and scheduling (i.e., a state with an inspection frequency of every two years might inspect more than half of the dams in the first year, or greater than 100%, in order to take advantage of their close proximity).

The national average for the inspection of high-hazard potential dams has remained relatively steady over the reporting period of 1998 to 2017.

In comparing 2017 to 1998, 32 states reported inspection activity for high-hazard potential dams equal to or greater than 100% of the 1998 level with an additional seven states at 75% or greater (percentages int he range of 75% and above would likely represent no significant decrease in inspection activity due to scheduling fluctuations).

Identification and Remeediation of Deficient High-Hazard Potential Dams
Increased inspection efforts by the state programs have resulted in the significant increase in the number of identified deficient high-hazard potential dams. The fact that there was not a corresponding large increase in the number of high-hazard potential dams remediated shows the need for increased enforcement efforts by state and for new rehabilitation and repair funding sources.

In 2009 the NID began collecting condition rating data on high-hazard potential dams. Those with Poor or Unsatisfactory ratings are considered in need of remediation. For the 2016 NID update, 85% of state-regulated high-hazard potential dams were rated. States voluntarily submit this data, and the number of dams not rated continues to decrease.

From 2009 to 2016 there was a 36 percentage point increase (34% to 70%) in dams with either a Satisfactory or Fair rating. The percentage of dams with condition ratings of Poor and Unsatisfactory (those in need of remediation) increased eight points from 7% to 15% as more dams were rated (Graph 8).

Note: 2010 and 2016 data from NID condition assessment with only 66% (2010) and 85% (2016) of state regulated HHP dams being reported. Prior years' data were anectodal totals reported by each state to ASDSO. The condition assessment field, instituted by the NID in 2009, will provide more accurate information on remediation needs than the anecdotal totals as the states report condition assessments for all HHP dams in coming years. More state and national statistics are available from the National Inventory of Dams.

National Dam Safety Awareness Day occurs each year on May 31 to commemorate the failure of the South Fork Dam in Johnstown, Pennsylvania on May 31, 1889.

National Dam Safety Awareness Day was created to encourage and promote individual and community responsibility and best practices for dam safety, and what steps people can take to either prevent future catastrophic dam failures or lessen the impact if a failure was to occur. Another important goal of National Dam Safety Awareness Day is to promote the benefits that dams offer.